Recently, the semiconductor material is widely applied in the electronic device, the integral circuits, and the solid lighting device. According to FIG. 1, the epitaxial defects 14, such as dislocations, usually occur in the epitaxial process due to the lattice constant mismatch between the substrate 10 and the semiconductor stack layer 12 in the semiconductor device 100. These epitaxial defects deeply affect the electrical property of the semiconductor materials and lower the reliability of the semiconductor device.
With reference to FIG. 2, there is a buffer layer 22 on the substrate 20 of the semiconductor device 200, wherein the lattice constant of the buffer layer 20 is matched with the lattice constant of the substrate, to overcome the aforementioned epitaxial defects problems. However, there are still some dislocations extending through the buffer layer 22 to the semiconductor stack layer 26.
FIGS. 3A and 3B show another manufacturing process of the conventional semiconductor device 300. The manufacturing process of the conventional semiconductor device 300 comprises, with reference to FIG. 3A, providing a substrate 30 and forming several buffer bodies 32 on the substrate 30, and then forming a buffer layer 34 on the substrate 30 and the buffer bodies 32, wherein the material of the buffer body 32 is amorphous, such as SiO2 and SiNx, and the buffer layer 34 is semiconductor. Because the buffer layer 34 can not grow on the amorphous buffer body 32, the buffer layer 34, according to the arrow a, grows vertically on the surface of substrate where is not covered by the buffer body 32 in advance, and then the buffer layer 34 grows laterally and covers the buffer body 32 when the thickness of the buffer layer 34 is larger than that of the buffer body 32. Subsequently, the semiconductor stack layer 36 is formed on the buffer layer 34 according to FIG. 3B. During the aforementioned epitaxial process, there are several epitaxial defects formed. The epitaxial defects are formed from the substrate surface which is not covered by the buffer body 32 and then bends with the growth direction of the buffer layer 32 to reduce the epitaxial defects of the semiconductor stack layer 36.
Although the technique mentioned above is capable of reducing epitaxial defects during the epitaxial process, there are still some defects extending from the buffer layer to the semiconductor stack layer to affect the electrical property and reliability of the semiconductor device.